Purpose To study the agreement between proton microdosimetric distributions measured with a silicon-based cylindrical microdosimeter and a previously published analytical microdosimetric model based on Geant4-DNA in-water Monte Carlo simulations for low energy proton beams. Methods and material Distributions for lineal energy (y) are measured for four proton monoenergetic beams with nominal energies from 2.0 MeV to 4.5 MeV, with a tissue equivalent proportional counter (TEPC) and a silicon-based microdosimeter. The actual energy for protons traversing the silicon-based microdosimeter is simulated with SRIM. Monoenergetic beams with these energies are simulated with Geant4-DNA code by simulating a water cylinder site of dimensions equal to those of the microdosimeter. The microdosimeter response is calibrated by using the distribution peaks obtained from the TEPC. Analytical calculations for y ¯ F and y ¯ D using our methodology based on spherical sites are also performed choosing the equivalent sphere to be checked against experimental results. Results Distributions for y at silicon are converted into tissue equivalent and compared to the Geant4-DNA simulated, yielding maximum deviations of 1.03% for y ¯ F and 1.17% for y ¯ D . Our analytical method generates maximum deviations of 1.29% and 3.33%, respectively, with respect to experimental results. Conclusion Simulations in Geant4-DNA with ideal cylindrical sites in liquid water produce similar results to the measurements in an actual silicon-based cylindrical microdosimeter properly calibrated. The found agreement suggests the possibility to experimentally verify the calculated clinical y ¯ D with our analytical method.

中文翻译：

---

使用硅基微剂量计对基于 Geant4-DNA 模拟的分析微剂量模型进行实验验证

目的 研究硅基圆柱形微剂量计测量的质子微剂量分布与之前发布的基于 Geant4-DNA 低能质子束水内蒙特卡罗模拟的分析微剂量分布模型之间的一致性。方法和材料 使用组织等效正比计数器 (TEPC) 和硅基微剂量计测量标称能量为 2.0 MeV 至 4.5 MeV 的四个质子单能束的线能量 (y) 分布。使用 SRIM 模拟穿过硅基微剂量计的质子的实际能量。通过模拟尺寸等于微剂量计尺寸的水缸位置，使用 Geant4-DNA 代码模拟具有这些能量的单能光束。使用从 TEPC 获得的分布峰来校准微剂量计响应。还使用我们基于球形位点的方法对 y ´ F 和 y ´ D 进行了分析计算，并选择要根据实验结果进行检查的等效球体。结果 硅上 y 的分布被转换为组织当量，并与模拟的 Geant4-DNA 进行比较，得到 y F 的最大偏差为 1.03%，y D 的最大偏差为 1.17%。我们的分析方法与实验结果的最大偏差分别为 1.29% 和 3.33%。结论 在液态水中具有理想圆柱形位点的 Geant4-DNA 中的模拟产生了与正确校准的实际硅基圆柱形微剂量计中的测量结果类似的结果。所发现的一致性表明可以用我们的分析方法通过实验验证计算出的临床 y ́D 。